Production and recovery of ammonium sulfate



Sept. 22, 1953- R. s. oGlLvlE PRODUCTION AND RECOVERY OF AMMONIM SULFATE Filed May 9, 1949 IYINM m 0 JmDL m Patented Sept. 22,1953

PRODUCTION AND RECOVERY '0F AMMONIUM SULFATE Robert `S. Ogilvie, Bartlesville, kla., `eassiu'gfnor:to Phillips Petroleum Company,- va corporation of Delaware Application May v9, 1949, Serial `o."'92,198

(Cl. :23h-'1195) 3 Claims.

Thisinvention relates to the production .-of ammonium sulfate. In one of its aspects it relates to the vconcentration of ammonium sulfate. In one of its more specific aspects it relates to the concentration of a dilute ammonium sulfate solution and to the production of ammonium sulfate by the reaction between sulfuric acidan'd ammonia.

Ammonium sulfate may be vproduced in known processes by the reaction of ammonium carbon-Y ate` with calcium sulfate obtained from gypsum. Also, ammonium sulfate may be producedby the reaction of sulfuric acid. and ammonia. In 'the productionof ammonium sulfate by the gypsum process, that is, reaction between ammonium `carbonate and calcium sulfate', a dilute solution of ammonium sulfate is formed. This solution-usually contains from 1:0130 per .cent ammonium sulfate, which concentration is substantially below a saturated solution.. In order' to recover ammonium sulfate crystals such as are satisfac-w tory to .be used `as afertilizer, etc., the water sol-m vent must be Yevaporated to give a saturated solu-Y tion-,.or preferably aslurry of water andammonium sulfate suitable to be processed a crystal--Y lizer and ammonium sulfate crystal drier. A major cost item in producing ammonium `sulfate is the expense involved in evaporating thiswater. When sulfuric acid and ammonia are reacted to produce ammonium' sulfate considerable heatr of` reaction is. given on. This heat ofv reactionmay be, advantageously used to evaporate water so as?- to. concentrate an ammonium sulfate solution. Processes which off-er economic and eflicient methods of recovering: ammonium sulfate. crys tals `from dilute ammonium sulfate'solution: aire-y great steps forward in the art.

I. have invented a process for concentrating a dilute ammonium sulfate solution while at the same time producing ammonium sulfatel by the reaction of sulfuric acid with ammonia'. I bea lievethat. my processioiers an optimum methodI of concentrating and producing ammonium sulfate, sincemy process recovers heat". of' reaction produced bythe reaction. of sulurici acid with ammonium under optimum reaction and heat-re'-4 covery conditions.v The process of myV invention comprses-'evaporating water from a dilute" ammoniumv sulfate solution byA directly contacting saiddilute ammonium sulfate solution withhot' products formed by the combustion of a mixture of vfuel gas and an oxygen-containing gas inthe` same reaction zone wherein sulfuric acid is neu'- tralized with gaseous ammonia. The -direct` contacty ofhot' products of combustion and aI dilute ammonium sulfate solution 4is :preferably accom-v plished by the use of a submerged burner, en-v abliln'g" vme 'to' direct fhot :products yof combustion down into the dilute ammonium sulfate solution. I :find that submerged burner evaporation gives extremely high thermal .efficiency ,and very .goed agitata-'iony to effect the Vreaction between sulfuric acid .and ammonia .as well as lto l.effect evaporation .of water y.through the' recovery of the heatv of reaction formed when sulfuric acid isl neutralized with. ammonia.- The :process of my in vention is .easy to .control :and :the amount `of equipment necessary :to carry Vout the process of my' invention isv at- .a 4miniminn `because of the h-ilghthermal' .eiiiciency which` vI obtain. In a prefer-red` embodiment o'f .my invention, I- react ammonium carbonate andl calciumsuflfate top-ro-A duce a dilute .aqueous :solution of ammonium sulfate, and recover `crystals of ammonium .-sulfate from .this .dilute .solution by the procedure just discussed;-

An object Aof thisyinven'tionis vtov v.produce fam'- monium. sulfate.I

Another object .of this invention is to concentrate a dilutef ammonium sulfate solution sor as toi prepare .a saturated solution or an rammonium sulfate-waterslurry suitable for cr-yStalIiZing, recoveringll anddry-ing annno'nium'` sulfate crystals.

Still another objecty of my .invention isy to pro-` vide a very economia; eiiicient ,and easy to control methodofl recovering ammonium sulfate fromia dilute ammonium Sulfate` solution Whilev at the same timev recovering ammoniumv Vsulfate produced by the' neutralizationof" sulfuric acid withV u Zmmlar Other' objects? andi advantages of: my invention will become apparent. to one skilled in the art, upon reading this' disclosure.`

The? drawing',.whichK accompanies and isf a part of this` disclosure, is'- a diagrammatic iicw sheetsetting# forth` alpreferredf specific embodiment of the process off my invention-.-

The following preferred specific embcdimentv of? 'my inve'ntion is set forthr to teacnone skilled inthearthow'to practice the' process ofi-myV invention.` Reierencefisimadet@ the1 drawing.;A A dilute-2 aqueous ammonium'v sulfate solution is passed via line' ll to' reaction and/orconcentration zone' 2;'- which contains a vapor zone above of ammonium 'sulfate and water, butl ispreferably The 1 and usually a dilute ammonium sulfate solution containing from to 30 weight per cent a.; monium sulfate produced by the so-ca-lled gypsum process, that is, by the reaction of ammonium carbonate with calcium sulfate. Ammonium sulfate solution may be introduced into reaction zone 2 at any suitable point, but since as hereinafter set forth ammonia gas is introduced into the lower portion of the liquid zone contained in reaction zone 2, I prefer to introduce the solution into the upperA 2/,. portion of the liquid zone. Fuel gas is supplied via lines 5 and 'l to header 9. Air or an oxygen-containing gas is supplied via lines H and I3 to header 9. The fuel gas and air or the fuel gas and an oxygencontaining gas are mixed, and are passed via line l5 down into submerged burner It wherein the mixture is burned. The hot flue gases resulting from the burning directly contact the liquid giving up heat and evaporating water. Water vapor plus cooled combustion products are withdrawn overhead from reaction zone 2. Submerged burner it may, of course, be a nest of burners as well as a single burner,

Ammonia is passed into reaction Zone 2 via line i9 and sulfuric acid is passed into reaction zone 2 via line 2l. The sulfuric acid is preferably introduced at a point above the point of introduction of ammonia. Gaseous and/ or liquid ammonia may be used, but it is preferred that gaseous ammonia be passed into reaction zone 2. While a gas stream containing ammonia and inert materials, such as coke oven gas, may be used as a source of ammonia to react with the sulfuric acid, I prefer to use ammonia of at least 90 weight per cent purity or, better still, substantially anhydrous ammonia. Introduction of inert gases, contained in the ammonia stream, which must be withdrawn overhead from reaction zone 2, should be kept at a minimum since their presence has been found to cause problems of spewing liquid out of the top of reaction zone 2. Also, water introduced must be evaporated since it will dilute the ammonium sulfate solution passed into reaction zone 2 and that ammonium sulfate formed by the reaction of ammonia and sulfuric acid. The presence of water and/or inert gases in the ammonia stream tends to lower the capacity of given equipment. The sulfuric acid introduced via line 2i may be dilute sulfuric acid but of course water present must be evaporated necessitating the use of more fuel gas and larger equipment for the production of a given quantity of ammonium sulfate. I prefer to use sulfuric acid of at least 90 weight per cent purity. I have found it preferable to introduce gaseous ammonia into the lower 1/3I portion of the liquid zone contained in reaction zone 2 and to introduce the sulfuric acid to the lower portion of the upper portion of said liquid zone. Under these preferred conditions of introduction, good reaction between ammonia and sulfuric acid is obtained.

The process of my invention may be carried out completely in reaction and/ or concentration zone 2, but as will hereinafter be set forth, I prefer to use a concentration zone following reaction zone 2. I prefer to use a subsequent concentration Zone because of the plugging difficulties encountered with the ammonia vapor distributing device in the lower portion of the liquid zone contained in reaction zone 2. I iind that it is desirable to operate reaction zone 2 so as to produce an ammonium sulfate solution which is no more than saturated. Ammonium sulfate crystals tend to plug up ammonia vapor distributing devices, necessitating shut-down time to unplug the equipment. If the process of my invention is carried out completely in reaction and/or concentration zone 2, the ammonium sulfate solution is preferably concentrated to a slurry suitable for further crystallization, recovery and drying of ammonium sulfate crystals. I prefer that this slurry contain 'l5-80 total weight per cent ammonium sulfate. This slurryis withdrawn from reaction zone 2 via lines 23 and 25 for further processing.

As hereinbefore set forth I prefer to use a concentration zone in conjunction with reaction zone 2. If such a concentration zone is used, a nearly saturated solution of ammonium sulfate and water is withdrawn from reaction zone 2 via line 23, and passed via lines 23 and 2'! into concentration zone 29. 'Ihe ammonium sulfate solution passed into concentration zone 29 should contain at least enough ammonium sulfate so that by water evaporation from concentration zone 29, the solution may be concentrated enough to prepare same for crystallization and recovery of ammonium sulfate crystals. I prefer that the solution withdrawn from reaction zone and passed into concentration zone 2t contain from 3G to 50 weight per cent ammonium sulfate. Concentration zone 2S contains a vapor zone above a liquid zone. Dotted line 3l indicates the interface between the upper vapor zone and the lower liquid zone. Fuel gas is supplied via lines 5 and y33 to header itt, and air or an oxygen-containing gas is supplied via lines il and 37 to header 35. Fuel gas and oxygen-containing gas are mixed, and are passed via line 38 to submerged burner 3H, one or more burners, wherein the mixture is burned. 'Ihe resulting hot products of combustion directly contact the liquid contained in concentration zone 29. The heat content of the hot combustion products is used to evaporate water as in reaction or concentration zone 2. Water vapor in admixture with combustion products of fuel combustion are withdrawn overhead from concentration zone 2S. An ammonium sulfate water slurry is withdrawn from concentration zone 29 via line 39 and is passed to suitable crystallizing, recovering and drying equipment. rIhis withdrawn slurry preferably contains from 75-80 total Weight per cent ammonium sulfate.

In carrying on the process of my invention any fuel gas, or available hot ue gases, may be used in the submerged burner, direct contact, step of my process. However, I prefer to use a fuel gas having a heating value of from 750-1250 B. t. u./ ft.3 net, determined at 60 F. and 760 mm. of mercury. It is desirable to use as good a fuel gas as possible since high gas volume creates problems of liquid spewing over the top of reaction zone 2 and concentration zone 2S. Also, I nnd it advisable to use no more than 25 per cent eX- cess air or oxygen-containing gas for the reasons set forth above.

The process of my invention may be practiced with several reactors and/ or concentrators operating in parallel, yand if desired, more than two stages of concentration may be used.

The process of my invention may be controlled manually or automatically. However, I prefer to control the process of my invention by the use of automatic liquid level controllers it and ill to maintain a constant liquid level in reaction and/or concentration zone 2 and concentration zone 2Q, respectively. Automatic fuel gas and air controllers i2 and 43 are used in conjunction with accom? liquid ileve'l controllers 140 .and JAI i'to control lthe amount of ffuel `:gas :and f air sory oxygen-containing gas passed `to headers fS and '35, respectively. These fuel gas andair controllers are setby the temperature ofthe ammonium sulfatesolutionor slurry withdrawn from'reaction .and/or concentration -zone :2 .and vconcentration zone 29. The total concentration of ammonium f sulfate kvin :the solution orv slurryL can 'be' correlated with the -temperature of the solution or slurry, fthe control valves regulating the fuel gas-and air-'beingsetby this temperature For instance, .if while main.- taining -a constant liquid level in reaction zone-2 not enough evaporation vis taking place, shown byf-the Elowering of ythe temperature of the :solution or slurry leaving reaction zone i2, Ythe =tem perature controller` would open the fuel gas and air valves, 'thus YYevaporating more Water. 1n operating automatically using the liquid level controllers Vand the fuel gas and air controllers, the dilute ammonium sulfate solution feed rate is preferably maintained constant as is the feed rate of sulfuric acid and ammonia. ofcourse, the tempera-ture control point may be inthe reactionand/ or concentration zone proper.

`If desired, means may be used yto addgammonia cr v'sulfuric Vacid to the solution or slurry Tpassed to concentration zone 29, if an excess of either is present dueto excess Aammonia or sulfuric acid being .added to reaction zone .2 or due to incomplete neutralization .in reaction zone v2. Of course, ammonia or sulphuricacid may be added to concentration Zonet@ to serve the same purpose. The ammonia or `sulfuric acid may conveniently loe-automatically added through `the-use of a control valve set by the pH of the solution or slurry.

Following is an example of the process of my invention. Reference is made to the drawing.

The quantities, concentrations, temperatures,'

pressures, etc., set forth are not to be deemed to unduly limit the scope of my invention. A dilute ammonium sulfate water solution is passed via line I to reaction zone 2 at the rate of 101.7 tons per day. This solution contains 19.4 weight per cent ammonium sulfate and has a temperature of 199 F. Gaseous ammonia, under a pressure of 50 pounds per square inch gage and at a temperature of 150 F., is passed into reaction zone 2 Via line E9 at a rate of 9.87 tons per day. This ammonia gas contains 99.7 weight per cent ammonia. Sulfurie acid is passed into reaction zone 2 via line 2| at a rate of 28.9 tons per day. This sulfuric acid is 98.0 weight per cent pure and has a temperature of 60 F. Ammonia gas passing up through the liquid Zone reacts with sulfuric acid to produce ammonium sulfate.

Fuel gas, having a heating value of 875 B. t. u./ ft.3 net determined at 60 F. and 760 mm. of mercury, is passed via lines and 'E into header 0 at a flow rate of 39,000 ft.3 per day, calculated at 60 F. and '760 mm. of mercury. Air is passed via lines II and I3 into header il at a rate of 430,000 ft.3 per day calculated at 60 F. and 760 mm. of mercury. Fuel gas and air are mixed and burned in submerged burner It, and the hot products of combustion are passed into the liquid contained in reaction zone 2.

An ammonium sulfate solution, containing 47.8 weight per cent ammonium sulfate and at a temperature of 220 F., is withdrawn from reaction zone 2 via line 23 and is passed via lines 23 and 21 into concentration zone 20. Fuel gas having the same net heating value as that passed to header 9 is passed via lines 5 and 33 to header 35at::aurate of '995000 .ftaper day,.calculatedsat 60 1F.fand760;mm..of mercury. Airata rateof 1,090,000 ft.3/olay, calculated ,at 60 F. and 76.0 mm. of .mercur.y, :is passed .via :lines 'LI I :andill into header 3.5. The air and fuel gasare mixed and burned 1in .submerged :burner '30, and the A'hot products of :combustion are passedfintotheliquid contained in concentration zone .2.9. Water vaporfevaporated and products of fuelcombustion are Withdrawnoverhead from concentration zonei.

sAn ammonium sulfate slurry containing 76.2 total weight per cent ammonium sulfate iswithdrawn'from concentration .zone "29 via .line '39. This 'withdrawn slurry has a temperature Vof 227 F. l

`AThe overall output of .ammonium sulfate Tis 57.9 tons per day and-the overall thermal eiciencyof fthe'process is 92 per cent.

`As will kbe evident lto those skilled in the art, Various 'modifications of this invention can `be made, or followed, inthe light of the foregoing disclosure and discussion, Without departing from the spirit or scopeof the disclosure or from the scope ,of the claims.

I claim:

1. ,Aprocess fortheproduction and concentration of yammonium sulfate .whichcomprised passinga Water solutionof `ammonium sulfate containingfrom vl0 to 30 weight percent ammonium sulfate into the upper 2/3 `portion cfa liquid Zone containedin areactionzonegsaid reaction zone containing .a vapor zone above said liquid zone, burning Within said liquid zone av combustible mixture of fuel gas, having a heating value of from 750 to 1250 Btu/ft.3 net at 60 F. and 760 mm. of mercury, and air, said air being present in said mixture in an amount not exceeding 25 volume per cent more than that required to completely combust said fuel gas, directly contacting said Water solution of ammonium sulfate and resulting hot products of said burning in said liquid zone so as to evaporate water from said solution, withdrawing water vapor from said vapor zone, introducing gaseous ammonia having a purity of at least weight per cent into the lower 1/3 portion of said liquid zone, introducing sulfuric acid having a purity of at least 90 weight per cent into the lower portion of the upper 2/3 portion of said liquid zone, reacting ammonia with sulfuric acid in said liquid Zone to produce ammonium sulfate, withdrawing a water solution of ammonium sulfate from the lower portion of said liquid zone containing fromV 30 to 50 Weight per cent ammonium sulfate, such Water solution containing no crystallized ammonium sulfate, introducing said Withdrawn ammonium sulfate solution into the upper 273 portion of a liquid zone contained in a concentration zone, said concentration zone containing a vapor zone above said liquid zone, burning within said liquid zone a second combustible mixture of fuel gas, having a heating value of from 750 to 1250 B.t.u./ft.3 net at 60 F. and 760 mm. of mercury, and air, directly contacting said last-mentioned ammonium sulfate solution and resulting hot products of said last-mentioned burning in the last said liquid zone so as to evaporate water, withdrawing water vapor from the upper portion of the last said vapor zone, and withdrawing an ammonium sulfate-Water slurry from the bottom portion of the last said liquid zone containing from 7 5-80 weight per cent total ammonium sulfate.

2. A process for the production and concentration of ammonium sulfate which comprises, passing a water solution of ammonium sulfate containing from 10 to 30 weight per cent ammonium sulfate into the upper 2/3 portion of a liquid zone contained in a reaction zone, said reaction zone containing a vapor zone above said liquid zone, burning within said liquid zone a combustible mixture of fuel gas, having a heating value of from 750 to 1250 B.t.u./ft.3 net at 60 F. and 760 mm. of mercury, and air, said air being present in said mixture in an amount not exceeding 25 Volume per cent more than that required to completely combust said fuel gas, directly contacting said water solution of ammonium sulfate and resulting hot products of said burning in said liquid zone so as to evaporate water from said solution, withdrawing water vapor from said vapor zone, introducing gaseous ammonia having a purity of at least 90 weight per cent into the lower 1/3 portion of said liquid zone, introducing sulfuric acid having a purity of at least 90 weight per cent into the lower portion of the upper 2/3 portion of said liquid zone, reacting said ammonia with said sulfuric acid in said liquid zone to produce ammonium sulfate, and withdrawing an ammonium sulfate-water slurry from the bottom portion of said liquid zone containing from 75-80 weight per cent total ammonium sulfate.

3. A process for the production and concentration of ammonium sulfate which comprises, passing a water solution of ammonium sulfate containing from 10 to 30 weight per cent ammonium sulfate into the upper 2/3 portion of a liquid zone contained in a reaction zone, said reaction Zone containing a vapor Zone above said liquid zone, burning within said liquid zone a combustible mixture of fuel gas and air, directly contacting said water solution of ammonium sulfate and resulting hot products of said burning in said liquid zone so as to evaporate water from said solution, withdrawing water vapor from said vapor zone, introducing gaseous ammonia having a purity of at least 99 weight per cent into the lower 1/3 portion of said liquid zone, introducing sulfuric acid having a purity of at least 90 weight per cent into the lower portion of the upper 2/3 portion of said liquid zone, reacting said ammonia with said sulfuric acid in said liquid zone to produce ammonium sulfate, and withdrawing an ammonium sulfate-water slurry from the bottom portion of Said liquid Zone containing from 75-30 weight per cent total ammonium sulfate.

ROBERT S. OGILVIE.

FOREIGN PATENTS Country Date Great Britain Sept. 5, 1935 OTHER REFERENCES Mellor, Treatise on Inorganic and Theoretical Chemistry, 1922, vol. 2, pages 694 and 695.

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1. A PROCESS FOR THE PRODUCTION AND CONCENTRATION OF AMMONIUM SULFATE WHICH COMPRISES, PASSING A WATER SOLUTION OF AMMONIUM SULFATE CONTAINING FROM 10 TO 30 WEIGHT PER CENT AMMONIUM SULFATE INTO THE UPPER 2/3 PORTION OF A LIQUID ZONE CONTAINED IN A REACTION ZONE, SAID REACTION ZONE CONTAINING A VAPOR ZONE ABOVE SAID LIQUID ZONE, BURNING WITHIN SAID LIQUID ZONE A COMBUSTIBLE MIXTURE OF FUEL GAS, HAVING A HEATING VALUE OF FROM 750 TO 1250 B.T.U./FT.3 NET AT 60* F. AND 760 MM. OF MERCURY, AND AIR, SAID AIR BEING PRESENT IN SAID MIXTURE IN AN AMOUNT NOT EXCEEDING 25 VOLUME PER CENT MORE THAN THAT REQUIRED TO COMPLETELY COMBUST SAID FUEL GAS, DIRECTLY CONTACTING SAID WATER SOLUTION OF AMMONIUM SULFATE AND RESULTING HOT PRODUCTS OF SAID BURNING IN SAID LIQUID ZONE SO AS THE VAPORATE WATER FROM SAID SOLUTION, WITHDRAWING WATER VAPOR FROM SAID VAPOR ZONE, INTRODUCING GASEOUS AMMONIA HAVING A PURITY OF AT LEAST 90 WEIGHT PER CENT INTO THE LOWER 1/3 PORTION OF SAID LIQUID ZONE, INTRODUCING SULFURIC ACID HAVING A PURITY OF AT LEAST 90 WEIGHT PER CENT INTO THE LOWER PORTION OF THE UPPER 2/3 PORTION OF SAID LIQUID ZONE, REACTING AMMONIA WITH SULFURIC ACID IN SAID LIQUID ZONE TO PRODUCE AMMONIUM SULFATE, WITHDRAWING A WATER SOLUTION OF AMMONIUM SULFATE FROM THE LOWER PORTION OF SAID LIQUID ZONE CONTAINING FROM 30 TO 50 WEIGHT PER CENT AMMONIUM SULFATE, SUCH WATER SOLUTION CONTAINING NO CRYSTALLIZED AMMONIUM SULFATE, INTRODUCING SAID WITHDRAWN AMMONIUM SULFATE SOLUTION INTO THE UPPER 2/3 PORTION OF A LIQUID ZONE CONTAINED IN A CONCENTRATION ZONE, SAID CONCENTRATION ZONE CONTAINING A VAPOR ZONE ABOVE SAID LIQUID ZONE, BURNING WITHIN SAID LIQUID ZONE A SECOND COMBUSTIBLE MIXTURE OF FUEL GAS, HAVING A HEATING VALUE OF FROM 750 TO 1250 B.T.U./FT.3 NET AT 60* F. AND 760 MM. OF MERCURY, AND AIR, DIRECTLY CONTACTING SAID LAST-MENTIONED AMMONIUM SULFATE SOLUTION AND RESULTING HOT PRODUCTS OF SAID LAST-MENTIONED BURNING IN THE LAST SAID LIQUID ZONE SO AS TO EVAPORATE WATER, WITHDRAWING WATER VAPOR FROM THE UPPER PORTION OF THE LAST SAID VAPOR ZONE, AND WITHDRAWING AN AMMONIUM SULFATE-WATER SLURRY FROM THE BOTTOM PORTION OF THE LAST SAID LIQUID ZONE CONTAINING FROM 75-80 WEIGHT PER CENT TOTAL AMMONIUM SULFATE. 